Case IH 3842 – ENGINE ECU: Turbine upstream temperature sensor: SRC High for turbine upstream temperature sensor

The physical signal from the exhaust gas temperature (EGT) sensor located just before the turbocharger (upstream) is reading excessively high. This typically means the sensor circuit is experiencing a short circuit to an external voltage source, an open circuit, or the sensor itself has internally failed and is returning a voltage above the maximum allowable limit.

• Farmall
• skid steer
• Maxxum
• skid steers
• compact track loaders

1. 1

   Visually inspect the turbine upstream temperature sensor on the exhaust manifold and its wiring harness for melted insulation, chafing, or physical damage.

2. 2

   Disconnect the sensor and inspect the pins on both the sensor and harness sides for corrosion, bent pins, or moisture ingress.

3. 3

   Test the sensor's resistance (Ohms) across its terminals; an open circuit or dead short indicates a failed sensor.

4. 4

   Turn the key to the ON position (engine off) and check the harness side for proper reference voltage (usually 5V) and a good ground. Battery voltage (12V+) on the signal wire indicates a short-to-power.

5. 5

   Check continuity from the sensor harness connector back to the Engine ECU pins to ensure there is no break in the wire.

1. 1

   Safety First

   Ensure the machine is turned off, the battery is disconnected, and the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Disconnect

   Unplug the electrical connector from the faulty turbine upstream temperature sensor.

3. 3

   Removal

   Spray penetrating oil (like WD-40 or PB Blaster) on the base of the sensor threads and let it sit. Use a properly sized wrench or an EGT sensor socket to carefully unthread the sensor from the exhaust manifold/turbo inlet elbow.

4. 4

   Preparation

   Inspect the threaded port on the exhaust pipe for damaged threads. Clean if necessary. Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (avoid getting any on the sensor probe itself, as this can ruin it).

5. 5

   Installation

   Thread the new sensor in by hand to prevent cross-threading, then tighten it to the OEM torque specification.

6. 6

   Reconnect

   Plug the electrical connector back into the engine harness. Ensure it clicks and locks securely.

7. 7

   Clear Codes

   Reconnect the battery, turn the key on, and use a CNH diagnostic tool (EST) to clear the inactive 3842 fault code. Start the engine and verify the code does not return.